The present invention relates to an optically variable surface pattern having at least two partial regions with reflection elements, wherein the reflection elements of the first partial region on the one hand and the reflection elements of the second partial region on the other hand reflect impinging light in different reflection directions.
DE 10 2010 047 250 A1 shows such an optically variable surface pattern, wherein the reflection elements are configured as embossed micro-mirror structures, to which a color-shifting layer can be applied. The color-shifting layer can be configured in particular as a thin-film interference coating.
Further, optically variable security features are known, which, upon tilting, present a kinetic effect in combination with a color change to a viewer. In the banknote area, for example the effect ink SPARK of the Swiss company SICPA HOLDING SA is widespread. This ink is based on platelet-shaped pigments which are coated with a thin-film interference system and are magnetically oriented after printing. Here, the “rolling bar” effect is particularly well known, where the pigments are so oriented that for example upon tilting a bright bar runs up and down within a value number, also changing its color while doing so. The color-change effect is based on the thin-film interference system of the pigments here.
The described interference coatings are usually a layer system of absorber/dielectric/reflector (e.g. ═Cr/SiO2/Al), which is vapor-deposited under a vacuum for example by means of electron-beam vaporization. These vaporization processes are comparatively expensive, since the different layers frequently must also be applied in respectively separate operations. The effort becomes particularly great when for example even a coating on both sides is required for the manufacture of corresponding effect pigments.
It is further known to produce color changes through cholesteric liquid crystals. However, these are comparatively faintly luminous and are sufficiently visible mostly only against a dark background.